Modeling the Electrical Discharge Machining process

Abstract

Electrical Discharge Machining (EDM) is a non-conventional machining process where material removal is achieved by electro-thermal energy. Since its discovery nearly 40 years ago, it has steadily gained importance and it is believed to account for over 2% of all machining. Machining in EDM is achieved by a series of microsparks produced by the breakdown of a liquid dielectric in a narrow gap subjected to high voltage. Physical understanding and modeling of these machines have lagged behind significantly their extensive use in industry. A computer simulation of the EDM process is essential for the prediction and optimization of erosion rates in these machines. A statistical mechanical model to estimate Equilibrium Thermophysical Properties of Oil Plasma for temperatures up to 60,000 K has been developed. These properties are required to calculate the temperatures and pressures of the plasma channel that develops during the on-time. Experiments on a wire-cutting Machine were performed to acquire data on Wire Breakage, a critical economic parameter in wire-cutting Machines. The factors responsible for the breakage of the wire during machining were identified. A computer model was developed to predict wire breakage. The model is also capable of predicting the amount of wire bowing, another problem associated with wire electrical discharge machining. The three models developed independently for the cathode, anode and plasma were combined into one program allowing for the power fractions to be functions of temperature. This made these existing models numerically more consistent with each other. Experiments to acquire erosion rate data were performed on a wire-cutting machine. These data were used to validate the model developed.